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        <h1>
          <span class="m-breadcrumb"><a href="namespacetf.html">tf</a>::<wbr/></span>AsyncTask <span class="m-thin">class</span>
        </h1>
        <p>class to create a dependent asynchronous task</p>
        <nav class="m-block m-default">
          <h3>Contents</h3>
          <ul>
            <li>
              Reference
              <ul>
                <li><a href="#typeless-methods">Constructors, destructors, conversion operators</a></li>
                <li><a href="#pub-methods">Public functions</a></li>
              </ul>
            </li>
          </ul>
        </nav>
<p>A <a href="classtf_1_1AsyncTask.html" class="m-doc">tf::<wbr />AsyncTask</a> is a lightweight handle that retains <em>shared</em> ownership of a dependent async task created by an executor. This shared ownership ensures that the async task remains alive when adding it to the dependency list of another async task, thus avoiding the classical <a href="https://en.wikipedia.org/wiki/ABA_problem">ABA problem</a>.</p><pre class="m-code"><span class="c1">// main thread retains shared ownership of async task A</span>
<span class="n">tf</span><span class="o">::</span><span class="n">AsyncTask</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">executor</span><span class="p">.</span><span class="n">silent_dependent_async</span><span class="p">([](){});</span><span class="w"></span>

<span class="c1">// task A remains alive (i.e., at least one ref count by the main thread) </span>
<span class="c1">// when being added to the dependency list of async task B</span>
<span class="n">tf</span><span class="o">::</span><span class="n">AsyncTask</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">executor</span><span class="p">.</span><span class="n">silent_dependent_async</span><span class="p">([](){},</span><span class="w"> </span><span class="n">A</span><span class="p">);</span><span class="w"></span></pre><p>Currently, <a href="classtf_1_1AsyncTask.html" class="m-doc">tf::<wbr />AsyncTask</a> is implemented based on the logic of C++ smart pointer <a href="http://en.cppreference.com/w/cpp/memory/shared_ptr.html" class="m-doc-external">std::<wbr />shared_ptr</a> and is considered cheap to copy or move as long as only a handful of objects own it. When a worker completes an async task, it will remove the task from the executor, decrementing the number of shared owners by one. If that counter reaches zero, the task is destroyed.</p>
        <section id="typeless-methods">
          <h2><a href="#typeless-methods">Constructors, destructors, conversion operators</a></h2>
          <dl class="m-doc">
            <dt id="a68689c79c7d794a8be2e1c181c818001">
              <span class="m-doc-wrap-bumper"><a href="#a68689c79c7d794a8be2e1c181c818001" class="m-doc-self">AsyncTask</a>(</span><span class="m-doc-wrap">) <span class="m-label m-flat m-info">defaulted</span></span>
            </dt>
            <dd>constructs an empty task handle</dd>
            <dt id="a148ddcabda8fd44746b278499cd4cb53">
              <span class="m-doc-wrap-bumper"><a href="#a148ddcabda8fd44746b278499cd4cb53" class="m-doc-self">~AsyncTask</a>(</span><span class="m-doc-wrap">)</span>
            </dt>
            <dd>destroys the managed asynchronous task if this is the last owner</dd>
            <dt id="a682bc679a773da5e45714f71c8137f70">
              <span class="m-doc-wrap-bumper"><a href="#a682bc679a773da5e45714f71c8137f70" class="m-doc-self">AsyncTask</a>(</span><span class="m-doc-wrap">const <a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp; rhs)</span>
            </dt>
            <dd>constructs an asynchronous task that shares ownership of <code>rhs</code></dd>
            <dt id="a5a31f85d2ee542f62e784d551ec78896">
              <span class="m-doc-wrap-bumper"><a href="#a5a31f85d2ee542f62e784d551ec78896" class="m-doc-self">AsyncTask</a>(</span><span class="m-doc-wrap"><a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp;&amp; rhs)</span>
            </dt>
            <dd>move-constructs an asynchronous task from <code>rhs</code></dd>
          </dl>
        </section>
        <section id="pub-methods">
          <h2><a href="#pub-methods">Public functions</a></h2>
          <dl class="m-doc">
            <dt>
              <span class="m-doc-wrap-bumper">auto <a href="#a14fa18d27a02c41e01b48ea07e87f5c5" class="m-doc">operator=</a>(</span><span class="m-doc-wrap">const <a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp; rhs) -&gt; <a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp;</span>
            </dt>
            <dd>copy-assigns the asynchronous task from <code>rhs</code></dd>
            <dt>
              <span class="m-doc-wrap-bumper">auto <a href="#a8dc18d17f3a5d72ef4d9c20ebf7ade4a" class="m-doc">operator=</a>(</span><span class="m-doc-wrap"><a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp;&amp; rhs) -&gt; <a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp;</span>
            </dt>
            <dd>move-assigns the asynchronous task from <code>rhs</code></dd>
            <dt id="ae42c70dc0c5edc6d58f47b346125fca3">
              <span class="m-doc-wrap-bumper">auto <a href="#ae42c70dc0c5edc6d58f47b346125fca3" class="m-doc-self">empty</a>(</span><span class="m-doc-wrap">) const -&gt; bool</span>
            </dt>
            <dd>checks if the asynchronous task stores nothing</dd>
            <dt id="a7c12835577fbdc1bca3190cf92c78088">
              <span class="m-doc-wrap-bumper">void <a href="#a7c12835577fbdc1bca3190cf92c78088" class="m-doc-self">reset</a>(</span><span class="m-doc-wrap">)</span>
            </dt>
            <dd>release the managed object of <code>this</code></dd>
            <dt id="a826a2ea909094f5a26c2df876de58056">
              <span class="m-doc-wrap-bumper">auto <a href="#a826a2ea909094f5a26c2df876de58056" class="m-doc-self">hash_value</a>(</span><span class="m-doc-wrap">) const -&gt; size_t</span>
            </dt>
            <dd>obtains a hash value of this asynchronous task</dd>
            <dt id="a6a4a54030f57d1ef05c04ae01825165d">
              <span class="m-doc-wrap-bumper">auto <a href="#a6a4a54030f57d1ef05c04ae01825165d" class="m-doc-self">use_count</a>(</span><span class="m-doc-wrap">) const -&gt; size_t</span>
            </dt>
            <dd>returns the number of shared owners that are currently managing this asynchronous task</dd>
            <dt id="aefeefa30d7cafdfbb7dc8def542e8e51">
              <span class="m-doc-wrap-bumper">auto <a href="#aefeefa30d7cafdfbb7dc8def542e8e51" class="m-doc-self">is_done</a>(</span><span class="m-doc-wrap">) const -&gt; bool</span>
            </dt>
            <dd>returns the boolean indicating whether the async task is done</dd>
          </dl>
        </section>
        <section>
          <h2>Function documentation</h2>
          <section class="m-doc-details" id="a14fa18d27a02c41e01b48ea07e87f5c5"><div>
            <h3>
              <span class="m-doc-wrap-bumper"><a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp; tf::<wbr />AsyncTask::<wbr /></span><span class="m-doc-wrap"><span class="m-doc-wrap-bumper"><a href="#a14fa18d27a02c41e01b48ea07e87f5c5" class="m-doc-self">operator=</a>(</span><span class="m-doc-wrap">const <a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp; rhs)</span></span>
            </h3>
            <p>copy-assigns the asynchronous task from <code>rhs</code></p>
<p>Releases the managed object of <code>this</code> and retains a new shared ownership of <code>rhs</code>.</p>
          </div></section>
          <section class="m-doc-details" id="a8dc18d17f3a5d72ef4d9c20ebf7ade4a"><div>
            <h3>
              <span class="m-doc-wrap-bumper"><a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp; tf::<wbr />AsyncTask::<wbr /></span><span class="m-doc-wrap"><span class="m-doc-wrap-bumper"><a href="#a8dc18d17f3a5d72ef4d9c20ebf7ade4a" class="m-doc-self">operator=</a>(</span><span class="m-doc-wrap"><a href="classtf_1_1AsyncTask.html" class="m-doc">AsyncTask</a>&amp;&amp; rhs)</span></span>
            </h3>
            <p>move-assigns the asynchronous task from <code>rhs</code></p>
<p>Releases the managed object of <code>this</code> and takes over the ownership of <code>rhs</code>.</p>
          </div></section>
        </section>
      </div>
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